Balo concentric sclerosis is often a distinct demyelinating syndrome. Dr. Kaufman argues that no clear evidence differentiates Balo concentric sclerosis from other acute, aggressive forms of multiple sclerosis. He discusses how the spectrum of Balo concentric sclerosis has changed with the discovery of nonfatal cases by magnetic resonance imaging. In addition, Dr. Kaufman describes its spectrum of symptoms and provides the current concepts behind the formation of its rings. In this update, he speculates that much about the mechanism of tissue destruction in multiple sclerosis may be inferred from pathological observations in Balo concentric sclerosis.

Key points

Balo concentric sclerosis shares features with other forms of acute demyelination associated with the development of multiple sclerosis.

Many cases with a Balo concentric sclerosis pattern noted by magnetic resonance imaging do not progress to multiple sclerosis and have a limited course.

The concentric ring pattern of Balo concentric sclerosis may be explained by activated microglia and macrophages migrating centrifugally and concentrating in rings for which spacing and activation state is determined by an inhomogeneous diffusion of chemokines and cytokines.

Activated microglia and macrophages release nitric oxide and oxygen radicals, which may inhibit complex IV of cytochrome c oxidase, leading to failure of energy production and cell death. This might be a hyperacute form of a pathology often associated with multiple sclerosis.